I was recently updating my home lab and ran into an issue with my NICs as VMware no longer has the Realtek 8168 drivers embedded in the ESXi installer for 5.5/6.0. I tried the old method of injecting the driver into the ISO and that proved unsuccessful since the driver is blacklisted -- with the release of vSphere 6.0 VMware has implemented a driver blacklisting feature. Fortunately you can bypass this feature to get your home lab up and running:

Unsupported VIB Installation Steps

Download driver offline bundle from VIBsDepot (at the very bottom of the page)

Upload the zip file to a datastore on your ESXi host using the vSphere Client

Enable SSH on the ESXi host (Refer to KB2004746 if needed) & login to the host using a SSH client

You now need to lower the VIB acceptance level to install this Community Supported VIB by executing the following command:

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esxcli software acceptance set--level=CommunitySupported

Now you can install your driver by executing the following command: (Replacing [DATASTORE-NAME] with the name of the datastore you uploaded the zip file to)